No wolf pups were counted on Isle Royale this winter, leading biologists to question whether inbreeding in the small population is affecting reproduction.

“This is the first year since 1971, the year reproduction first began being monitored, that we did not detect any sign that pups had been born during the past year,” John Vucetich, Michigan Technological University population biologist, said in the school’s 2012-13 Isle Royale study released this week.

Researchers counted eight wolves, down one from last year, on the Lake Superior island located north of the Upper Peninsula’s Keweenaw Peninsula…